Premature sensence
of t- lymphocytes in patients with β
-thalassemia
The
umbrella term ‘immunosenescence’ is
applied to describe age-associated failing systemic immunity and is believed to
contribute to the increased incidence and severity of infectious disease in old
animals and people .The
immunosenescence is considered as a complex remodeling of lymphocyte subpopulation
and function, caused normally by aging in elderly people or prematurely by
various chronic inflammatory.
T
lymphocytes become specialized in the thymus gland to play a pivotal role in
conducting the adaptive immune orchestra resulting in cellular immunity (via CD8
cytotoxic T cells) and B cell-mediated humoral immunity. T cells are considered
to be highly vulnerable to the ‘effects’ of ageing. A number of factors have been linked to the decline
in T cell function with age; however, it appears that chronic age-induced
thymic atrophy and resultant decreased output of native T cells is the most
important factor [2].
As
somatic cells, the proliferative potential of T cells is restricted. It is not
exactly known how many cell cycles a T cell can complete. Because T cells have
the ability to upregulate telomerase, they may be able to prolong their life span
(Chiu and Harley, 1997; Shiels et al., 1999; Liu et al., 1999; Son et al.,
2000). However, after repeated divisions, they enter a program of cellular
senescence.
Cellular
senescence is characterized by three cardinal features :
(1) altered function, e.g.
production of large amounts of inflammatory cytokines.
(2) shortening of telomeric sequences
and, eventually, proliferative arrest.
(3)
resistance to apoptosis (Campisi, 1996, 2001a,b).
Dr.Nada Fathy
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